This invention relates to musk odorants and precursors thereof. More specifically it relates to acetylated mixtures of polyalkylindanes and polyalkyltetralines prepared from a suitable aromatic compound having the p-cymene skeleton and a mixture of alkenes consisting of one or more methylbutene isomers and one or more dimethylbutene isomers.
Through the years considerable effort has been made to arrive at synthetic products exhibiting desirable musk like odors. Typical representatives of such musk odorants belong the class of acetylpolyalkylindanes and acetylpolyalkyltetralines, both with a wide variety of the substitution pattern in the aromatic moiety as well as in the nonaromatic moiety of the molecule. Amongst them are, for example, the commercially successful aroma chemicals Phantolid (R), i.e., 6-acetyl-1,1,2,3,3,5-hexamethylindane and Tonalid (R), i.e., 7-acetyl-1,1,3,4,4,6-hexamethyltetraline, prepared by acetylation of the corresponding hexamethylindane and hexamethyltetraline, respectively, which in turn are prepared by cycloalkylation of usually p-cymene with usually 2-methyl-2-butene and 3,3-dimethylbutene-1, respectively, yielding the said aroma chemicals at purity levels of 95% and above.
Some methods of preparation of polyalkylindanes and polyalkyltetralines are set forth in German patent application 1035826, U.S. Pat. No. 2,759,022, Swiss patent 336377, German patent 1243187, European patent application 89207 and Japanese patent application 8240420 starting from substituted benzenes and aliphatic alkenes, aliphatic alcohols or aliphatic halogenides in the presence of sulphuric acid or Friedel-Crafts catalyst. In U.S. Pat. Nos. 2,851,501, 3,278,621, 3,379,782, 3,379,783, 3,379,784 and 3,379,785, European patent application 61267 and Japanese patent application 7363757 methods of preparation of cycloalkylated aromatic compounds are described starting from substituted isopropenylbenzenes and aliphatic alkenes or alphatic alcohols in the presence of Lewis acids, proton acids, activated clays or cation exchange resins.
In the U.S. Pat. Nos. 3,246,044, 4,740,646 and Japanese patent application 8275935 the use of substituted or unsubstituted benzyl halides is disclosed as the aromatic reactant in combination with aliphatic alkenes and in the presence of Lewis acid catalysts.
In U.S. Pat. Nos. 4,551,573 and 4,877,912 cycloalkylations catalyzed by aluminum halides and elemental iodine are set forth. In U.S. Pat. No. 3,856,875 a process is claimed for the preparation of 1,1,3,4,4,6-hexamethyl-l,2,3,4-tetrahydronaphtalene which comprises reacting p-cymene with a substantially equimolar solution of 3,3-dimethylbutene-1 and t-alkylhalide in the presence of an effective amount of an aluminum halide catalyst suspended in a reaction compatible solvent. In U.S. Pat. No. 4,284,818 the utilization of alkyl halides is extended to the combination of p-cymene and a 2,3-dimethylbutene in an aliphatic hydrocarbon or cyclohexane solvent. In Japanese patent application 8143221 a similar method of preparation is disclosed for 1,1,3,4,4,6-hexamethyltetraline utilizing a mixture of p-cymene, 3,3-dimethylbutene-1 and an essentially equimolar amount of a primary alkyl chloride, e.g., isobutyl chloride. The combination of alkenes and alkyl halides is also the subject of U.S. Pat. Nos. 4,877,910, 4,877,911, 4,877,914 and 4,877,916. European patent 393742 describes a process starting from a benzyl alcohol and an alkene under the influence of a Lewis acid. In U.S. Pat. Nos. 4,877,910, 4,877,912, 4,877,913, 4,877915 and 4,877,916 the cycloalkylation of substituted benzenes by specific alkenes in the presence of specific olefinic reagents with greater electron releasing properties is set forth.
The acetylation of polyalkylindanes and polyalkyltetralines can be carried out by methods known to the art, e.g., by the interaction with acetic anhydride or an acetyl halide and a suitable catalyst and, for example, according to the methods set forth in European patent applications 89207 and 393742, French patent 8519207 and U.S. Pat. Nos. 3,045,047 and 4,162,256.